Technology update

Feb 7, 2014

CNT e-whiskers could help improve robot skin

Researchers at the University of California at Berkeley have fabricated highly sensitive lightweight electronic whiskers from carbon nanotubes and silver nanoparticle composite films that can detect the lightest of touches or a gentle breeze. The whisker sensors are the first of their kind because previous such devices were made using bulky torque and force sensors on micro- to millimetre-sized fibres. The structures might be placed on robot “skin” in the future and in human-machine interfacing, says the team.

Animals use their whiskers to detect wind and to navigate around obstacles. The new electronic, or e-whiskers, made by Ali Javey’s team, could be the next best thing to their natural counterparts in terms of size and weight. The researchers fabricated them by painting composite films of carbon nanotubes (CNTs) and silver nanoparticles (AgNPs) onto high-aspect-ratio elastic fibres made of the polymer PDMA. The CNT “paste” forms a conductive network matrix that can be bent and unbent at will without suffering any damage. The AgNPs further increase the conductivity of the composite and make it highly sensitive to strain at the same time.

The composition of the ensemble can be easily tuned by modulating the amount of the CNTs and AgNPs.

When the e-whiskers detect a light touch or a gentle breeze they bend and their resistance changes dramatically. The structures are sensitive to pressure changes of just 8% – the highest value reported to date for such tactile sensors.

Better balanced robots

If mounted into arrays, the whiskers could be placed on robotic e-skin so that the robots are better able to navigate. They could also be used in human-machine interfaces, says team member Zhibin Yu. “They might even be ideal for some medical applications, for example, in devices that monitor heartbeat and blood pressure,” he told nanotechweb.org.

The Berkeley team says that it is now looking to make the devices using different printing processes and produce them on a larger scale.

Structures such as these that mimic biological systems could help in the development of so-called smart and user-interactive electronics, explains Yu. Researchers have already succeeded in fabricating rudimentary e-skin and e-eyes by engineering novel materials and devices onto thin, flexible substrates so that the most ordinary of materials can now “feel” and “see” their environment. “Electronic whiskers are another important class of sensor, capable of monitoring surrounding airflow and touch,” he said. “They can also spatially map nearby objects (just like naturally occurring whiskers) – a property that might help improve balance in robots of the future.”